Conversion of olefins to gasoline and/or distillate product is disclosed in U.S. Pat. Nos. 3,960,978 and 4,021,502 (Givens, Plank and Rosinski) wherein gaseous olefins in the range of ethylene to pentene, either alone or in admixture with paraffins, are converted into an olefinic gasoline blending stock by contacting the olefins with a catalyst bed made up of ZSM-5 or related zeolite. In U.S. Pat. Nos. 4,150,062 and 4,227,992 Garwood et al discloses the operating conditions for the Mobil Olefin to Gasoline/Distillate (MOGD) process for selective conversion of C.sub.3 + olefins. A fluidized bed process for converting ethene-containing light olefinic streams, sometimes referred to as the Mobil Olefin to Gasoline (MOG) process is described by Avidan et al in U.S. Patent Application No. 006,407, filed 23 Jan. 1987 now U.S. Pat. No. 4,746,762. The phenomena of shape-selective polymerization are discussed by Garwood in ACS Symposium Series No. 218, Intrazeolite Chemistry, "Conversion of C.sub.2 -C.sub.10 to Higher Olefins over Synthetic Zeolite ZSM-5", 1983 American Chemical Society. U.S. Pat. No. 3,827,968 (Givens et al) discloses a two stage operation wherein a mixed feed containing paraffins and olefins is upgraded in the absence of added hydrogen to a highly aromatic gasoline product. In a first stage oligomerization reaction, olefins are upgraded to higher molecular weight liquid hydrocarbons under relatively mild conditions with a catalyst having the structure of ZSM-5. In a second stage, said liquid hydrocarbons are converted to an aromatic product. A gas phase highly paraffinic stream is withdrawn as by-product from the first stage.
In the process for catalytic conversion of olefins to heavier hydrocarbons by catalytic oligomerization using an acid crystalline metallosilicate zeolite, such as ZSM-5 or related shape selective catalyst, process conditions can be varied to favor the formation of either gasoline or distillate range products. In the gasoline operating mode, or MOG reactor system, ethylene and the other lower olefins are catalytically oligomerized at elevated temperature and moderate pressure. Under these conditions ethylene conversion rate is greatly increased and lower olefin oligomerization is nearly complete to produce an olefinic gasoline comprising hexene, heptene, octene and other C.sub.6 + hydrocarbons in good yield.
The olefins contained in an FCC gas plant are an advantageous feed for MOG. U.S. Pat. No. 4,090,949 discloses upgrading olefinic gasoline by conversion in the presence of carbon hydrogen-contributing fragments including olefins and a zeolite catalyst and where the contributing olefins may be obtained from a gas plant. U.S. Pat. Nos. 4,471,147 and 4,504,691 disclose an MOG/D process using an olefinic feedstock derived from FCC effluent. In these two latter patents the first step involves prefractionating the olefinic feedstock to obtain a gaseous stream rich in ethylene and a liquid stream containing C.sub.3 + olefin.
The conventional MOG process design is concerned with converting ethylene in a fuel gas stream, such as an FCC off-gas, to gasoline. Motor octane of the gasoline produced is generally about 85. Typically, paraffins conversion under MOG process conditions is not significant thereby constraining the utilization of potential feedstocks available from FCC operations and requiring substantial recycle of paraffins to the FCC main column.
Accordingly, it is an object of this invention to provide a process for the conversion of mixtures of paraffins and olefins to high octane gasoline incorporating the conversion of paraffins and olefins.
It is another object of the present invention to provide a process for the production of high octane gasoline rich in alkylated aromatics.
Yet another object of the present invention is to provide a process for the production of gasoline with higher olefin conversion.
Another object of the instant invention is to provide a novel reactor system for the conversion of paraffinic and olefinic hydrocarbon mixtures to high octane gasoline rich in aromatics.